Extend naming conventions with things to avoid

[elbrujohalcon]

Currently, our naming convention rules only allow for a single regex that identifies what is permitted/valid.
It would be nice to add an additional forbidden regex to identify things that are not valid, like function names starting with do_.

Ref: WhatsApp/erlfmt#91

[paulo-ferraz-oliveira]

For semantics purposes, a forbidden keyword might make sense... but then you'd always have to have an order in evaluation: if you accept and negate a given string, which one is valid?

Have you considered negative lookaheads, like ^(?!(^do_)).*$?

> {ok,RE} = re:compile("^(?!do_).*$").
{ok,{re_pattern,0,0,0,
                <<69,82,67,80,87,0,0,0,16,0,0,0,1,128,0,0,255,255,255,
                  255,255,255,...>>}}
> re:run("ado_", RE).                        
{match,[{0,4}]}
> re:run("do_", RE). 
nomatch

[elbrujohalcon]

HA! I didn't know about negative lookaheads.
I still think that a forbidden regex would be clearer and the usual semantics is "allow everything that matches with regex except if it matches forbidden regex". I would go with that, with the default for forbidden being none.

[paulo-ferraz-oliveira]

with the default for forbidden being none.

It could even be undefined :-)

[bormilan]

Could you help me with the regexes? What do we want to add to the forbidden regexes?
We have four naming conventions, function_, variable_, module_, and atom_naming_convention.

[elbrujohalcon]

@bormilan the default should be none or undefined or something that means nothing.
As examples of forbidden regexes (for tests), you can use… say… "[0-9]" if you don't want numbers at all in your… atoms (maybe). Or you can exclude specific words, like "(is|maybe|do)". Or you may want to forbid names ending with an underscore, i.e. "_$". Use whatever expression you want as a regex example, be creative!

[bormilan]

Oh, I understand now; the goal is to allow users to specify their forbidden cases if they wish, rather than adding specific rules.
Thanks!

[paulo-ferraz-oliveira]

... and make it explicit in the doc., as @elbrujohalcon states, that whatever is accepted in regex except if it matches forbidden.